The present invention relates to industrial fasteners and more particularly to a plastic hole plug (closure plug) used to close a hole in a wall panel which is backed by tape and foam insulation.
In the manufacture of various panels, especially thin plastic panels and sheet metal panels, holes are formed in the panel which are later to be filled by a screw, rivet or other fastener. However, frequently, the holes are left empty. For example, a refrigerator body consists of a thin interior plastic panel wall and an outer wall of metal. The space between them is filled with a solid plastic foam. This type of refrigerator wall construction is called a "foamed-in-place" construction because the foam is inserted, while in its liquid state, between the inner panel and the outer wall. The inner panel is formed with a series of holes, for example, the holes are located to receive screws to attach shelves or devices such as ice makers. If one or more devices are omitted, for example, the device may be an optional device which is not selected, the panel would be left with an empty hole. Generally, the hole should be closed, so that the panel may have a better appearance and to prevent the passage of moisture or dirt. The hole is covered by an adhesive tape and is backed by plastic foam.
A hole plug must be able to be retained in the panel; for example, it should stay in its hole after being installed even though the panel may vibrate or objects may be bumped against the plug. It is possible, but labor intensive and time consuming, to punch a hole in the tape and the foam behind the empty hole with with an awl or other sharp pointed tool and then to insert a hole plug. Preferably, however, the hole plug should be sufficiently sharp and stiff so that it forms its own hole in the foam, which requires only the one action of inserting the hole plug. The plug must be able to fit in holes which are not exactly round and in holes which are "off-size", i.e., either too big or too little for the exact diameter of the plug. Some hole plugs, which are satisfactory in other respects, may be expensive because they utilize an excessive amount of plastic resin or because their design requires expensive manufacturing techniques.